1. Technical Field
This disclosure relates generally to thin-film magnetoresistive read sensors and particularly to the use of configurations of two such sensors in a single read head to implement “two dimensional magnetic recording”.
2. Description
So called “two dimensional magnetic recording” promises increased areal density in HDD (hard disk drive) applications. This promise will be achieved by a means that include analysis of multiple readback signals from the same recorded track, instead of the conventional single readback signal used in current magnetic recording. Two dimensional magnetic recording is described in R. H. Victora et al., “Two-Dimensional Magnetic Recording at 10 Tbits/in2”. IEEE Transactions On Magnetics, Vol. 48, No. 5, May 2012. In addition, the design of read head arrays is also taught in Ikegami et al. (US Publ. Pat. Appl. 2007/0242378), Gao et al. (US Publ. Pat. Appl. 2012/0206830), Reinhart (EPO Pat. Appl. DE 3535671) and Kumar et al. (U.S. Pat. No. 7,239,570).
Advanced signal processing of the multiple read signals of a single HDD datatrack, and/or a portion of its neighboring track, allows for improved signal-to-noise and improved decoding of the written pattern. For HDD applications, the multiple readback signals can be acquired either by multiple reads of a single sensor, such as would be obtained by multiple passes produced by multiple disk rotations, or by the use of multi-sensor heads, or by a combination of both.
Space and tolerance constraints, among other issues, prohibit the construction of multiple sensor heads for real applications using conventional techniques. While the two dimensional recording concepts were first published over five years ago (see Y. Shiroishi, Intermag 2009, FA-01 and also, F. Lim et al., Intermag 2010), there have been no proposals for a practical multisensory head for realistic applications in a HDD to improve performance, with or without corresponding use of the two dimensional recording concepts. As a result, implementations have been restricted to those that require a multi-pass reading of recorded data, which brings with it serious cost and performance penalties. We note that the references indicated above, including descriptions of two dimensional recording in the various journals and conference proceedings and the several prior art references, do not contradict our assertions as to the present lack of viability of realistic multi-sensor arrays.